Machines for producing, filling and sealing sachets, which produce these sachets from a strip of material which is usually pressure and heat sealable and fill them with products of various kinds, for instance solids, liquids, powders or granules and other loose materials, are well known.
Machines of this type and for the above described usage to which the invention relates generally comprise a vertically extending operating structure and essentially comprise a frame or base and, supported on this base, a tube with a vertical spindle, a member in the form of a shaping collar disposed within this tube with a vertical spindle so as form an annular space thereby providing a kind of drawing member, means for supporting a spool of pressure and heat sealable material and for supplying the latter downwardly through this annular space between the shaping collar member and the tube with a vertical spindle and folding it into a tubular shape around and along the tube with the vertical spindle with its longitudinal edges overlapping, means for supplying the product to be packaged above this tube with the vertical spindle, drive means with an intermittent movement below this shaping collar member in contact with the tube with a vertical spindle designed to drive the strip intermittently downwards along the tube with a vertical spindle, the length of each intermittent movement being equivalent to the length of the sachet to be obtained, pressure and heat sealing means disposed along the tube with a vertical spindle at the level of the drive means with an intermittent movement and respectively below these latter means for pressure and heat sealing of the overlapping longitudinal edges of the strip and transversely to the tube of pressure and heat sealable material obtained in this way during the dwell period of each intermittent movement and means designed to actuate the pressure and heat sealing means alternately in conjunction with the dwell period of each intermittent movement.
In these known machines with an intermittent movement, the intermittently moving drive means are usually formed by two more or less vertically elongate closed-loop belts disposed diametrically with respect to the vertical tube. These belts are obviously synchronized for the intermittent downward drive movement of the strip folded into its tubular shape and a machine of this type with drive belts is known commercially as an intermittent "caterpillar" drive machine.
Like all machines operating with an intermittent movement, these machines with an intermittent movement for producing, filling and sealing sachets have unit output limits due not only to the dwell periods of the cyclical intermittent movements in which the operations leading to the formation of the desired product can be carried out, but also to the inertial forces of the moving components which make up the complex kinematic mechanism designed to achieve this intermittent movement. In the case of machines with an intermittent cycle of the type in question which comprise a sealing stage which, as is known, depends for its success not only on temperature and time, but also on the contact pressure of the sealing members with the pressure and heat sealable material, which is a non-negligible technical and commercial feature, these unit output limits are also due to the constructional complexity of the sealing members for the conduct of the pressure and heat sealing with variations in the operating speed of the machine.
In order to remedy these speed limits imposed by the mechanical structure of these machines for producing, filling and sealing sachets, the applicants have previously disclosed, in their Italian Patent Specification 1 145 089 analogous to the U.S. Pat. No. 4,524,567, a machine of this type operating with a continuous movement and structured so that the sealing contact time between the sealing members and the pressure and heat sealable material for the formation of the sachets varies to the required extent with variations in the unit output speed.
In order to achieve this, a machine of the type in question is characterized, in accordance with the above Italian Patent in the name of the applicants, in that the drive means and the pressure and heat sealing means for the pressure and heat sealing transverse to the tube of pressure and heat sealable material are associated with support means controlled by actuation means with a continuous movement below the tube with a vertical spindle, the drive means comprising two members having sectors with cylindrical surfaces counter-rotating tangentially with respect to a plane containing the axis of descent of this tube of pressure and heat sealable material and in which these drive means with a continuous movement are provided with a cyclical differentiating device for the transmission of this movement.
Machines of this type constructed in accordance with the above-mentioned Italian Patent 1 145 089 in the name of the applicants having drive means with a continuous movement, although achieving optimum results from the point of view of product quality and output speed per unit of time have in practice proved inadequate for achieving transverse pressure and heat seals when certain relatively thick pressure and heat sealing materials are used and in particular as a function of the features of their constituent structure.
Machines with an alternating movement of the type having a unit production speed of this kind and for the above-mentioned uses and having a vertically extending operating structure which take account, in addition to temperature and time, of the contact pressure between the sealing members and the pressure and heat sealable material are already known. For instance, the U.S. Pat. No. 4,040,237 of 18 June 1976 discloses a mechanism for forming pressure and heat seals or the like in adjacent layers of strip material as part of a method for forming packagings carried out by a machine comprising two jaws and means for slidably supporting and actuating the two jaws so as to move them between open and closed positions. One of the two jaws is fixed to a slide supported so as to slide with respect to a base along a given sliding axis and the other is supported slidably on a slide for the sliding movement along the same sliding axis. A crank mechanism simultaneously moves the slide and the other jaw in order to actuate the two jaws in opposite directions towards their open or closed positions depending on the direction of rotation of the crank. In the closing direction of the jaws the crank mechanism has a toggle action so as to provide a high closure force between the jaws causing the jaws to close gently with no recoil or violent impact.
These crank mechanisms with a toggle pressure action come within the scope of typically intermittent unit speed machines as a result of which they do not adequately satisfy the pressure requirement of faster machines with a vertical operating structure having drive means with a continuous movement, for instance of the type disclosed in the above-mentioned Italian Patent 1 145 089 in the name of the applicants.